Abstracts

Rationale: Magnetic source imaging (MSI) is integral to pre-surgical evaluations for pediatric epilepsy patients, as it yields data regarding localization of seizure onset and lateralization of cerebral language dominance. Delineating areas of eloquent cerebral cortex facilitates prediction of post-surgical language outcome. The current study presents MSI language lateralization data for the largest series of pediatric epilepsy patients thus far (n=34), including the youngest patients with valid MSI language lateralization data (age range=4 17 years). Clarifying characteristics of patients with atypical (i.e., non-left) language dominance allows for more accurate clinical interpretation of MSI data. Preliminary data analysis reveals recognizable patterns of relevant clinical features among patients with atypical language dominance.Methods: Data from 34 pediatric epilepsy patients (ages 4 17 years) was collected via retrospective record review. All patients were being considered for epilepsy surgery, due to focal intractable seizure disorder. All patients produced valid language lateralization data during the receptive language (CRM) task of the MSI protocol. The magnetoencephalography (MEG) unit consisted of a 148-channel Magnes 2500 WH system and data were analyzed using the single equivalent current dipole (ECD) model across each whole hemisphere. Handedness was determined using the Edinburgh Handedness Questionnaire. Mean age was 11 years (range=4 17). Twenty-seven patients were right-handed; 7 patients were left-handed. Six patients had FSIQ < 70. Twenty patients had primarily left-hemisphere seizure focus; 14 patients had primarily right-hemisphere seizure focus.Results: Sixteen (47%) patients demonstrated left cerebral hemisphere language dominance on MSI; 12 (35%) demonstrated bilateral language dominance; 6 (17%) demonstrated right language dominance. Of the 18 patients who showed atypical (non-left) language dominance: 15 (83%) had seizure onset < 5 years; 14 (78%) had duration of epilepsy > 4 years; 11 (61%) had primarily left hemisphere seizure focus; 7 (39%) were under age 8 years; 6 (33%) were left handed; 3 (17%) had FSIQ < 70.Conclusions: This study presents MSI language lateralization data for the largest pediatric epilepsy series reported to date, including the youngest patients with valid MSI language lateralization data. Preliminary data analysis implicates younger age at seizure onset, longer duration of epilepsy, and left hemisphere seizure focus as the most salient characteristics in the majority of patients with atypical language dominance on MSI.